Marijuana plants are seen in Chicago where officers say they discovered two football fields worth of pot plants growing on the city's South Side, Oct. 3, 2012. Authorities say about 1,500 cannabis plants were discovered during a routine patrol by a police helicopter. Officers spotted the crop under a canopy of trees about 3 miles from their own hangar. Some were as tall as Christmas Trees. Police said the growers could have earned as much as
$10 million.

(CBS/AP) CHICAGO - Police officers began to chop down 1,500 marijuana plants worth about $10 million on Wednesday after a police helicopter found the crops growing on a chunk of land the size of two football fields in Chicago's far South Side.

No arrests were made as police continue to investigate who owns the property. Police said that due to the large size of the operation, they are hopeful that information and tips will come forward about those involved, including a man seen running away from the area as the helicopter swooped low.

Cmdr. James O'Grady of the department's narcotics division said the property is unlike anything they've seen before due to Chicago's harsh winters providing a harsh environment for plants to grow compared to warmer climates such as California and Mexico. The bumper crop was likely planted in spring, O'Grady said.

O'Grady added that there are few spots in Chicago where such an operation could go unnoticed due to all the buildings, roads and residents. He said the growers must have taken pains to ensure their crop was largely hidden by a canopy of trees and surrounding vegetation.

Officer Stan Kuprianczyk, a pilot, said police helicopters previously flew over the area "all the time" to and from their hangar without noticing the grow site. Cook County Sheriff's Deputy Edward Graney said a number of factors including the right training enabled him to spot the plants.

"We had the right altitude, the right angle, the right sunlight, and I happened to be glancing down," Graney said. He said he initially spotted five plants or so through the trees before he asked Kuprianczyk to circle around for a closer look.

Graney said just a few weeks earlier, they had to fly over and videotape a smaller operation in suburban Chicago so they might be able to recognize marijuana if they ever saw it from the air again. By the time Graney spotted the marijuana plants on Wednesday, he had a pretty good idea what he was looking at.

Superintendent Garry McCarthy said the discovery of the marijuana is significant in a larger fight against street violence, in which narcotics distributors are known to purchase firearms with their profits and willing to use them to protect their business.

"That's where the violence comes in, the competition for the markets," he said.